Sweet Flag (Acorus calamus)

The Acorus calamus, otherwise known as Sweet Flag, is an amazing choice of vivarium plant to have in an enclosure or indoor/outdoor pond, with or without animals!

This plant is considered an aquascaping pond plant and can be utilized both in and out of the water, depending on the buildup.

Sweet flag is the perfect starter plant for any beginner hobbyist, as it’s easy to take care of and is safe for all pets and animals.

Quick Stats:
Scientific Name Acorus calamus
Common Name Sweet Flag, Calamus
Family Name Acoraceae
Habitat Swamps and streams
Temperature 55-85°F
Height 2-3 feet
pH 6.5-7.5
Lighting Moderate to Bright

What Is Sweet Flag?

The Acorus calamus is a plant native to wet areas around the world, including ponds, streams, and even swamps.

The plant is classified as an emergent aquatic grass and has an appearance resembling bamboo.

It grows to a height of 2 to 3 feet with lance-shaped leaves and thick parenchymous stems.

Sweet Flag has known to produce small, yellow-green flowers in the late spring and summer.

It isn’t considered to be significantly showy in comparison to some other aquatic plants

Acorus calamus "Sweet Flag" Plant Care Guide

Sweet Flag Facts

It is widely believed that the rootstock of the Acorus calamus was used to make teas and herbal incense in the past.

The root of this plant can also be eaten and has a pleasant, sweet taste.

The dried rootstock of this plant is still used in traditional and modern medicines to treat an array of digestive and respiratory issues.


The Acorus calamus consists of multiple, thick parenchymous stems that grow to a height of 2 to 3 feet.

This plant has lance-shaped leaves that are long and pointed, with a slight bend.

The leaves grow to approximately 16 inches in length by 3-4 inches in width and are a light green color with a hint of yellow.

The rootstock of this plant is highly aromatic and holds a unique, sweet smell. 


The Acorus calamus is a plant native to the wetlands of India, China, Thailand, and other warm climates.

This pond plant is often found in swamps and streams, taking advantage of the high temperatures and moist soil.

pH Preference

The Acorus calamus is an aquatic grass and does best in an alkaline environment.

This plant prefers a pH range between 6.5 and 7.5 for ideal growth.

It will do better near the higher end of this spectrum, but high levels of pH could prove detrimental to this plant.

Vivarium Type

Sweet Flag is quite an easy-going species.

With that in mind, it will not be too complicated when it comes to choosing the type of enclosure it is grown in.

It is best to try and replicate the plant’s natural habitat as much as possible.

Doing so will make it easier to provide this pond plant with its basic needs.

The proper setup and theme of the enclosure will make a big difference to the overall look and health of the plant.

Be sure to choose setups that are moist and high in humidity.

Here are recommended vivariums it will do well in:

  • Paludariums – Half aquatic/ half terrain-based enclosure.
  • Ripariums – Mostly aquatic-based enclosures with some terrain features present.
  • Terrariums – Fully terrain-based enclosures with little to no aquatic features.

Vivarium Placement

This plant can survive both in and out of the water, so placement options are wide open.

If planted outside of the water, you will want to make sure that the substrate is well-draining and that there is enough moisture to keep the roots hydrated.

The Sweet Flag Plant can also be planted in shallow containers of water or as part of an aquatic setup, as long as the water is not too low.

Make sure to adjust the water level to the best of your abilities. 


Having a well-draining aquatic substrate is essential for the growth of the Sweet Flag.

When planting this plant outside of the water, use a mix of terrarium gravel and soil that is rich in organic material.

The Sweet Flag also does well when planted in the sand, and this makes it ideal for vivariums that contain sand as the substrate.

When planting in water, be sure to use a fine substrate such as aquatic gravel or small-grained aquatic sand


For Sweet Flag to thrive, it needs medium to high light levels, ideally around 6500-8000 lux.

The best way to achieve this is to provide intense aquatic lighting or place the tank near natural sunlight.

If you are using bulb-style fixtures, provide a mix of LED and fluorescent light to achieve a bright and balanced light intensity.

Buy Sweet Flag

When buying an Acorus calamus, there are a few things to keep in mind.

Making sure the plant is healthy when purchased is essential for its success in a vivarium or pond.

Vegetation that is already in poor conditions will have a very hard time adjusting to new environments.

Click the image below to learn more about the current price and other relative info about this plant.

Sweet Flag Care & Propagation

The Acorus calamus is a pretty simple plant to care for, but it does require moderation.

In other words, it does not do well when exposed to extreme temperatures or constantly changing levels of water and pH.

Sweet flag propagation is fairly easy once it is established in its environment.

The stems of the plants can be manually divided with sharp pruning sheers, and each division will form a new plant. 

How To Grow

When propagating new growth, the soil needs to remain constantly moist for the new rosettes to form properly.

As roots form and new foliage grows, you may start reducing the amounts of water given, since the plant needs time to absorb the moisture and nutrients.

You may also see conditions where the foliage begins aging and eventually turns a deep, brown coloring.

Until this happens, continue providing adequate amounts of moisture so the plant may remain diseasefree.

Water Requirements

Sweet Flag is highly adaptable, so it can withstand a variety of water levels, from very wet conditions to occasional shallow flooding.

It is not drought tolerant, so consistent moisture is necessary for optimal growth and flowering.

Sweet Flag has a relatively high water requirement and should be kept consistently moist.

Especially during the warmer months when water evaporation rates are highest.

It is best to check the soil moisture level frequently and water when needed.

Plants Similar To Sweet Flag

Adding diversity to an enclosure is key to an aesthetically pleasing setup.

Try mixing up the look of your vivarium with different flora that can easily co-exist in the same types of environment.

Furthermore, if for some reason you find Sweet Flag hard to acquire or would like to consider something similar to this riparium plant

Here are other pond plants you might find will do well with or in place of Acorus calamus:

Alternanthera ficoidea "Party Time Plant" | The Care Guide
Coleus scutellarioides "Painted Nettle" Plant Care Guide
Ruellia brittoniana ‘Katie’ "Katie Ruellia" Plant Care Guide


The graceful and fragrant foliage of Sweet Flag provides a pleasant look to any terrarium.

Despite being a slow-growing species, it is a reasonably low-maintenance addition for any vivarium.

Sweet Flag has a wide range of colors and textures its foliage provides and requires only moderate lighting.

Though it needs decent amounts of water, it is also capable of surviving through dry periods and cold temperatures.

All in all, its strain of care needs and overall aesthetics, makes this plant a great indoor or outdoor addition.

Frequently Asked Questions

Acorus calamus is also traditionally used to treat a variety of ailments, including digestive and respiratory problems, inflammation, and skin conditions. It is also thought to help boost the immune system and act as a stimulant. In addition, it is used in Ayurveda, an ancient Indian system of healing, to improve digestion, reduce fever, and improve brain function.

Yes, Acorus calamus (sweet flag) is toxic and should not be consumed. It can cause adverse effects such as dizziness, vomiting, diarrhea and abdominal pain. It may also be toxic to certain animals.

Today, Calamus is known as Sweet Flag or Acorus calamus.

Possible side effects of Acorus calamus include nausea, vomiting, headache, dizziness, heart palpitations, skin reactions, and breathing problems. Longterm use of Acorus calamus has been linked to liver toxicity, changes in heart rate and blood pressure, and increased risk of certain cancers.

No, sweet flag grass (also known as Acorus calamus) is not considered an invasive species.

Yes, calamus is banned in many countries. It is prohibited from being used as a food or medicine due to concerns about its potentially toxic effects.

Acorus calamus is used in traditional medicine, but its usage is controversial as it contains toxic compounds. Its toxicity is potentially offset if used in low doses or preparations made from the root‘s rhizomes rather than from the leaves. Modern botanical studies have identified potential health benefits that may be derived from use of this medicinal plant, although further studies are needed to confirm these potential effects.

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